Sewage disposal septic tanks



July 25, 1967 R. ZABEL 3,332,552

SEWAGE DISPOSAL SEPTIC TANKS Filed Sept. 27, 1963 3 Sheets-Sheet 1 a -g y INVENTOR.

ROBERT L. ZABEL ATTORNEY July 25, 1967 R L. ZABEL SEWAGE DISPOSAL SEPTIC TANKS 5 Sheets-Sheet 2 Filed Sept. 27, 1965 INVENTOR. ROBERT L. ZABEL BY )nxfi m ATTORNEY July 25,

Filed Sept. 27, 1963 R. L. ZABEL 3,332,552

3 Sheets-Sheet 3k 1 C 372" LEVEL 5 L W 26 LEVEL L CZERO LEVEL l: 50

LOWEST INLET :LEVEL 5 STAGNANT [LEVEL 6 INVENTOR.

ROBERT L ZABEL ATTORNEY United States Patent 3,332,552 SEWAGE DISPOSAL SEPTIC TANKS Robert L. Zabel, 9315 Fairground Road, Fem Creek, Ky. 40021 Filed Sept. 27, 1963, Ser. No. 312,163 14 Claims. (Cl. 210- 86) My US. patent, #2,900,084, granted Aug. 18, 1959, discloses: (A) a septic tank having its interior arranged to provide a U-shapedpath of flow wherein (1) one leg of the U constitutes an upstream chamber which receives incoming sewage through a tank inlet at a high inlet level and is normally filled therewith up to an intermediate stagnant level spaced substantially (say 4.0) below the high inlet level and (2) the other leg of the U constitutes a downstream chamber which receives partly or completely digested sew-age from the upstream chamber through the bight of the U and is normally filled therewith up to said intermediate stagnant level and which discharges a clarified efiluent through the tank outlet as and when additional sewage pours into the upstream chamber and thus causes the downstream chamber to overflow its stagnant level; (B) a cylindrical casing vertically arranged within the outlet end portion of the tank to form the downstream chamber with an inlet opening at its bottom and with a side wall outlet at the top side of the stagnant level; and (C) an outlet trap arranged within the casing (1) to screen or strain solids from the fluid material overflowing the downstream chamher and (2) to provide an outlet passageway directing that overflow into the tank outlet.

The outlet trap shown in my patent comprises: 1) a heavy base-dam unit composed of (a) a horizontally elongate, sinuous, overflow dam which extends back and forth across a somewhat circular are proceeding from one side of the tank outlet to the other; (b) a concrete base plate supporting the dam and providing a shelf on vthe upstream side of the dam and the floor of the outlet passageway on the downstream side of the dam; and (2) an overlying member (a) cooperating with the upper edge of the dam to form a horizontally-elongate vertically-narrow outlet slot of substantial length and (b) pro,- viding an overhanging canopy on the upstream side of the dam and a ceiling for the outlet passageway on the downstream side of the dam. With this arrangement, the slot can be made extremely narrow and correspondingly eflicient in straining solids from the water and still provide an outlet opening of substantial water-passing capacity even when clogged with solids over a considerable portion of its length.

The principal object of the present invention is to improve my foregoing outlet trap in one or more of the following respects, viz: to effect a substantial increase in its discharge capacity, in the length of its maintenance free operation and in the purity of its eflluent; and to effect a substantial reduction in its liquid inlet velocity and in its tendency to clog.

Another important object is to accomplish the principal object in a simple, inexpensive and compactly constructed outlet trap of light weight which may be easily and quickly installed, which requires relatively little maintenance and which may be easily and quickly removed, inspected, cleaned and reinstalled or replaced.

Septic tanks are conventionally provided with outflow traps. No matter how satisfactorily these traps work, most of them will clog from time to time. The fact that a trap is clogged usually is discovered only after the stagnant level within the septic tank rises sufliciently above the lowest inlet level to prevent incoming sewage from flowing into the tank.

Another important object is to provide aseptic tank 3,332,552 Patented July 25, I967 with signaling means operative to indicate the desirability of cleaning the trap before it is clogged sufliciently to interfere with the flow of incoming sewage.

Most of the objects of my invention can be achieved by the following: (1) substituting, for the concrete base plate of my aforesaid base-dam unit, a thin lightweight disc, preferably composed of plastic, so that, it cooperates with the strip, to form a disc-dam unit; (2) forming a stack composed of a number of these disc-dam units arranged in vertically spaced superposed relationship such that the bottom of each overlying unit cooperates with the upper edge of each underlying unit to form a horizontally-elongate vertically-narrow outlet slot; and (3) mounting the stack within the cylindrical casing with several slots located above and several located below the stagnant level so that said stack not only divides the downstream chamber into two compartments, one receiving digested sewage through the bottom opening of the casing and the other discharging clarified eflluent through said side wall outlet, but also enables the receiving compartment to discharge into the discharge compartment through a large normally submerged area permitting flows below the stagnant level and another large normally unsubmerged area accommodating substantial overflow above the stagnant level.

I have found that when a stack of this character is mounted to submerge one or more slots below the stagnant level, the resulting increase in its discharge capacity effects a corresponding reduction in the velocity of flow through the outlet slots and, with this latter reduction, there is a substantial lessening of the tendency of the liquid flowing into the trap to carry solids with it; hence, there is a corresponding increase in the purity of its eflluent. The same is true when a stack of this character is mounted to provide several slots above the stagnant level.

I have also found that undigested solids tend to collect on the submerged shelves and to remain there undisturbed by the liquid which slowly passes through the outlet slots so that they are ultimately completely digested and thus converted into ash. Furthermore, by providing these shelves with a large number of perforations, the ash will ultimately sift downwardly through these openings rather than build up an ash deposit high enough to reach the slots. Finally, if the submerged slots and those within the normal overflow range of the trap become clogged, the stagnant level itself will rise to a point where its overflow can pass through the still higher slots so that the trap thereby continues to provide a satisfactory operation.

In further accordance with my invention, I make use of the rise in the stagnant level due to clogging to operate a signaling means which indicates the desirability of cleaning the trap before the trap is clogged sufliciently to interfere with the flow of incoming sewage. In this way, it becomes possible to maintain the trap continuously in a good operating condition and thereby prevent the development of the highly objectionable conditions which follow serious clogging.

The invention is illustrated in the accompanying drawing wherein:

FIG. 1 is a sectional view of a septic tank having an outlet trap made in accordance with my invention;

FIG. 2A is a vertical sectional view of a cylindrical casing, which forms the downstream chamber of the septic tank of FIG. 1, this view of the casing corresponding to one taken along line 2-2 of FIG. 3 but showing my improved outlet trap in elevation, the elevational view of the trap being broken away along the normal stagnant level to provide a vertical central sectional view through the partially submerged disc-dam unit along the stagnant level and the disc of the adjacent overlying normally unsubmerged disc-dam unit;

FIG. 2B is an enlarged fragmentary view of the partially submerged disc-dam unit along the normal stagnant level and the disc of the adjacent overlying normally unsu-bmerged disc-dam unit;

FIG. 3 is a top plan view of the structure shown in FIG. 2 with one half of the top disc (or lid) of the stack broken away;

FIG. 4 is a fragmentary perspective view showing details of the stack hanging brackets and the ash return holes;

FIG. is a somewhat schematic view of an alarm system which is associated with the trap; and

FIG. 6 is the circuit diagram of the alarm system.

CONVENTIONAL STRUCTURE FIG. 1 shows a septic tank 1 of conventional concrete construction which preferably is buried in the ground with its top preferably at a short distance below ground level. The top of the tank contains a pair of covers 2 and 3 normally closing a pair of 18" access openings. The sewage enters at one end of this tank through a conventional T-shaped fitting 4 having its lowest inlet level 5 located substantially (say 4") above the normal stagnant level 6 of the tank. The interior of tank 1 is conventionally arranged to provide a U-shaped path of flow.

One leg of the U constitutes a large upstream chamber 7 which receives incoming sewage through the tank inlet 4 and is normally filled therewith up to the normal stagnant level 6. The other leg of the U is in the form of a relatively small downstream chamber, which is provided at the outlet end of the tank 1 by cylindrical casing 8. Sewage, in various stages of digestion, flows from the upstream chamber 7 into the casing 8 through its open bottom end and it naturally fills that casing up to the normal stagnant level 6 of the tank 1.

IMPROVED OUTLET TRAP In accordance with my invention, the cylindrical casing 8 is made of any suitable plastic, preferably a thermoplastic such as polyethylene. The interior of the casing 8 is divided by my improved outlet trap into two compartments, one compartment 8A receiving sewage from the upstream chamber 7 and the other compartment 8B dis charging a clarified efiluent through the tank outlet 9 as and when additional sewage pours into the upstream chamber 7 and thereby causes the discharging compart- .ment 8B of easing 8 to overflow stagnant level 6. Before Each disc-dam unit is made of any suitable material, preferably any suitable plastic and even more preferably a thermoplastic. Each unit comprises: (A) a horizontally elongate sinuous overflow dam 12 which extends back and forth across a somewhat circular arc proceeding from a point 13 corresponding to one side of the tank outlet 9 to a point 14 corresponding to the other side of the outlet 9, this dam being in the form of a strip 12 arranged with its width extending vertically; and (B) a horizontally-arranged vertically-thin disc 15 supporting the dam.

The dam 12 extends to the periphery of the disc 15 at its end points 13 and 14; otherwise, it is spaced inwardly from the peripheral edge of the disc to form an upstream shalf 16 which, in accordance with a further feature of my invention, is'perforated at intervals to provide ash return holes 17. Preferably, the disc and dam are formed as one integral plastic unit and the upper edge of each reverse bend in the dam is provided with a plastic tip which projects upwardly a distance equal to the desired vertical Width of the outlet slots. In other words, for an elongate slot having a width of A of an inch, the tips 18 will project upwardly A of an inch.

Stack forming means A stack of these disc-dam units is formed by assembling a suitable number of these units in vertically-spaced superposed relationship such that the bottom of each overlying unit rests upon the top of the tips 18 and are thereby spaced from the upper edge of the dam of each underlying unit so as to cooperate therewith to form a horizontally-elongate vertically-narrow outlet slot 20. To hold the superposed units firmly in assembled relationship, a laterally-spaced pair of additional spacers 21 and 22 is arranged between each pair of disc-dam units. All of the spacers 21 are vertically aligned with each other and with corresponding holes in the stacked discs 15 to receive a rod 23 which is long enough to project from opposite ends of the stack. The projecting ends of rod 23 are provided with clamping nuts 24 which are screwed toward each other sufiiciently to clamp the assembly into a relatively firm stack. The other spacers 22 are similarly provided with a rod 25 having clamping nuts 26.

Stack mounting means The stack may be easily and quickly hung in its appropriate position by a pair of flat vertically arranged hanger bars 30, each bar having its upper end provided with a hook 31 to hook over the upper edge of the casing 8 and its inner vertical edge provided with a succession of vertically spaced notches 32, one notch for each disc 15, each notch providing a snug fit for the peripheral edge of its disc. These flat hanger bars 30 are horizontally dimensioned to force the stack horizontally in the general direction of the outlet 9 so as to press the points 13 and 14 of each disc tightly against the casing 8.

In this latter connection, it will be noted that the discs at the top and bottom ends of the stack function as the top and bottom closures of the discharging compartment 8B; hence, that portion of each end disc, which lies between-points 13 and 14 and corresponds to the outlet 9, has a peripheral edge circularly shaped so that it fits against the adjacent inner wall of the casing 8. The remaining or intermediate discs 15 have this corresponding portion out off, preferably along a straight line 15A between points 13 and 14, so as to provide the discharging compartment 8B with a vertical passageway, which com municates (a) on one side with the successive spaces provided within the interior of the stack by successive topcovered disc-dam units and (b) on its other side with the outlet of easing 8.

OPERATION In operation, sewage enters the septic tank 1 through the inlet fitting 4 and fills the upstream chamber 7 and the downstream chamber (i.e. the receiving and discharging compartments 8A and 8B) up to the normal stagnant level 6. When additional sewage pours into the upstream chamber 7, the stagnant level 6 in the downstream chamber will overflow correspondingly through outlet 9.

If we assume that 10 gallons of sewage comes into the tank, then the 10 gallons of liquid will flow from compartment 8A into 8B and 10 gallons will likewise overflow from compartment 8B into outlet 9. Most of the flow from the upstream compartment 8A will pass through the several normally-submerged outlet slots 20. However, the stagnant level 6 must rise to create and discharge the overflow. As a result of this rise, a small percentage of the 10 gallons will normally pass through the lowest unsubmerged outlet slot 20. Since the outlet slot area is large, the velocity of flow through any one slot is very low; hence, there is little tendency to stir up any solids or ash in receiving compartment 8A and carry them into com,-

partmetnt 8B. The efliuent discharging from compartment 8B should, therefore, be comparatively free of solids; hence, quite clear.

While most of the digestion will take place in the large upstream chamber, some digestion will necessarily take place in the downstream chamber. Most of the downstream digestion occurs in receiving compartment 8A. Some occurs in the discharging compartment 8B. In this connection, I have found that many of the undigested solids in the receiving compartment 8A tend to settle on the submerged upstream shelves 16. Once they have settled, I believe most of them remain there.

In observing the stack in operation, I have not seen any settled undigested solids move from the shelves 16. Furthermore, the large discharge area provided by the outlet slots makes is possible for a large Volume of liquid to be discharged from compartment 8A into compartment 8B in a relatively short time at a velocity so low that it has little or no effect upon either the undigested solids or the ash which may be deposited on the shelves. As a consequence, a deposit of undigested solids on the shelves 16 appears to stay there until it is digested and thus converted into ash.

I have found that the provision of perforations 17 in the upstream shelves 16 permit ash deposits on the shelves to sift downwardly through the shelves. When these perforations are closely spaced, they tend to prevent the deposits of solids from building up to the level of the adjacent outlet slots 20. Some of this sifting ash is bound to pass through the slots although it seems that very little of it does because the efiluent discharged from this unit is exceptionally clear.

Under some conditions of use, the submerged outlet slots 20 may become clogged sufliciently to minimize (or even prevent) the flow of liquid from compartment 8A to compartment 8B through the normally submerged slots 20. With my arrangement, however, this clogged condition will normally do nothing more than cause the stagnant liquid to rise above the stagnant level 6 of the upstream chamber 7 and the upstream compartment 8A (but not above level 6 of downstream compartment 83) until the rising level in compartment 8A reaches an open slot 20 at a higher level through which it can overflow into compartment 8B. In other words, some of the outlet slots, which normally are unsubmerged by the liquid in compartment 8A, will now become submerged by that liquid {but not by the likuid in compartment 8B) and they will thereafter operate as submerged slots over a period of time which depends upon the conditions of use.

During that time, the solids, which clog the normally submerged outlet slots, may be digested over an area large enough to restore operating conditions to normal. Again, it may be that the normally submerged outlet slots for the stagnant liquid remain clogged and that the lower normally unsubmerged (but now submerged) outlet slots for the overflow liquid begin to clog. In this latter event, the rising overflow level of 7 and 8A continues to rise to new overflow levels in compartment 8A. I make use of this excessive rise in the overflow level to operate a signaling means which indicates the desirability of cleaning the trap before it is clogged sufiiciently to interfere with the flow of incoming sewage and which may be sensed outside of the tank.

SIGNALING MEANS Any suitable form of signaling means responsive to an overflow of the stagnant level 6, either in the upstream chamber 7 or in the upstream compartment 8A, may be employed. Broadly stated, I prefer: signal means adapted, when actuated, to provide a warning signal which may be sensed outside of said septic tank. More particularly, I prefer the use of a simple float-controlled type of indicator and I prefer to locate it in the upstream receiving compartment 8A.

Accordingly, a float 35 is provided on the lower end of a plastic or other rod 36, which is slidably engaged by lower and upper guides 37 and 38 and which has its upper end at a non-signaling level when the liquid is at the normal stagnant level 6. In the arrangement shown, the upper end of the rod 36 projects through the cover 3 and through the upper guide 38, in the form of an upright guide sleeve 38 on cover 3, with its upper end about flush with the upper end of the sleeve. Now as the 8A overflow level rises above the stagnant level 6, the upper end of the rod 36 will correspondingly rise out of the top of sleeve 38 where it may be visually sensed outside of the tank.

If the vertical distance between the stagnant level 6 and the lowest inlet level 5 equals 4", the rod 36 must rise 4" before the trap is clogged to a dangerous degree. Consequently, by observing the extent to which the rod projects from sleeve 36 one can determine the precise extent to which the overflow level has risen above the normal stagnant level 6. Stated otherwise, when the upper end of the rod continuously projects 2 /2" from the upper end of sleeve 38, the observer will know that the trap is partially clogged but the clogging condition is not one requiring urgent attention. However, if the rod continuously projects 3 /2 from the upper end of sleeve 38, the observer will know that the trap is seriously clogged and should be given prompt attention in order to avoid the objectionable condition which begins with 4" rises in the overflow level.

While the foregoing silent signal arrangement is satisfactory, it may not be regularly observed. Since it may be overlooked, I prefer to provide a signaling means which is more likely to be sensed. Accordingly, I provide the property, which is serviced by the septic tank 1, with a signaling means which may (if desired) be located at a place where it is more likely to be sensed than is the upper end of the projecting rod 36. If the signaling means is to function as an early warning or caution signal, it may be of a silent type which calls silent but positive attention to itself when energized. On the other hand, if it is to signal an emergency condition requiring prompt attention, I prefer that it be audible. I

In the present case, it is a simple matter to accommodate both conditions. Accordingly, I provide a signaling means comprising: (a) a first signal; (b) first actuating means operative, when actuated, to energize said first signal; (c) first control means operative, in response to one order of rise of the overflow level, to actuate said first actuating means; (d) a second signal; (e) second actuating means operative, when actuated, to energize said second signal; and (f) second control means operative, in response to a greater order of rise of said overflow level, to actuate said second actuating means.

First signal The first signal may be of a suitable type. Preferably it is in the form of an electrically energizable illuminating signal such as an electric lamp 40'. The lamp 40 should be located in a frequently visited neighborhood where it will silently, yet positively, call attention to itself when energized. I recommend a prominent location in a frequently visited room such as a kitchen or hallway, or in a nearby utility room, closet or basement.

First actuating means The first actuating means for energizing the lamp 40 is preferably in the form of a normally-open switchcontrolled lamp circuit comprising: a source of power 41; a normally-open switch 42; and electric lines 43, 44 and 45 serially interconnecting the lamp 40, source of power 41 and normally open switch 42.

The normally open switch 42 may be of any suitable type. In the arrangement shown, it is of the normallyopen magnetically closable reed type. Such a switch 42 is mounted on the tank 1 proper adjacent the access opening which is normally closed by cover 3. The switch 42 is shown as mounted on a switch base 47, which may be embedded in the concrete forming the top wall of the tank 1. The switch base 47 holds the switch 42 in a position where it is close to the rod 36 but does not interfere with the up and down movement of the rod.

First control means The first control means may be of any suitable type. Preferably it is in the form of a magnetically permeable member; more particularly a permanent magnet 50 mounted on the rod 36 for movement with the rod. The rod 36 normally holds the upper end of the magnet 50 at the magnets zero elevation, i.e. the elevation which it occupies when the float is held at the stagnant level 6. At this zero elevation, the permanent magnet is unable to actuate the first control means. The magnet remains inoperative during the normal rising and falling movements of the rod under normal overflow conditions, which are assumed to be less than 2%".

However, when the overflow level rises, say 2 /2" above the stagnant level 6, the rod 36 and magnet 59 rise with it. Thus the magnet is raised to its 2 /2" warning elevation where it initially becomes effective to close the switch 42 and thereby actuate the first control means to energize the lamp 40.

With this arrangement, as long as the overflows are temporary and of insufiicient magnitude to raise the magnet 50 to its 2. /2" warning level, the lamp signal 40 remains inoperative. However, if the overflow level rises, even temporarily to the 2 /2" warning level, the switch 42 will operate the lamp signal 40. If this rise is temporary, the magnet will soon fall sufficiently below its 2 /2" warning level to permit switch 42 to reopen and thereby deenergize the lamp 40.

Consequently, upon seeing the lamp either continuously on or going on and off, the informed observer will know that the trap is partially clogged and that it may or may not require attention. If the lamp remains continuously energized, the observer will know that there is a partial blocking and possibly some attention should be paid to the trap. This partial blockage, however, is not one which necessarily requires immediate attention.

Second signal The second signal may be of any suitable type. Preferably it is an emergency signal of the audible type. Accordingly, a hell or buzzer 60 is provided and preferably mounted in the vicinity of the warning signal lamp 40.

Second actuating means The actuating means for energizing the emergency signal bell 60 comprises: said source of power 41; normallyopen magnetically-closable reed-type switch 62; and electric lines 43, 64 and 65 serially interconnecting the bell 60, source of power 41 and normally open switch 62.

The normally open switch 62 may be of any suitable type but preferably it is of the same'reed type as switch 42 and is mounted in the same way except at a higher elevation directly above switch 42.

Second control means The second control means may be of any suitable type. Preferably the same magnet 50 is used for this purpose. The control arrangement is such that, when the overflow level rises, say 3 /2" above the stagnant level 6, the magnet is thus raised to its 3 /2" emergency elevation where it initially becomes effective to close the switch 62 and thereby actuate the second actuating means to energize the bell 60.

When bell 60 rings, either continuously on or on" and off, the informed observer will know that the trap is seriously clogged and that it should be given prompt attention.

'8 MISCELLANEOUS It may be helpful to note that I have obtained excellent results: (a) with disc-dam units each having a darn long, a diameter of 9% and a maximum vertical dimension of wherein the vertical thickness of the disc 15 is /8", the height of the dam 12 is V2" and the height of the tips 18 is (b) with a stack composed of 20 disc-dam units (plus a top cover disc) and providing 20 outlets 80" long by wide, of which 6 are unsubmerged and 14 are submerged, whereby the stack has a diameter of 9%" and a height approximating 14"; and (c) a cylindrical casing 8 having a 12" diameter and an 18 height and arranged to holdthe stack with its ends spaced from the ends of the cylinder approximately 1 /2" at the top and 2 /2 at the bottom. A unit of this general character can be readily removed and replaced as a unit through the overlying 18" access opening under cover 3.

It will be understood that a permanent magnet may be associated with each or both of said reed type switches 42 and 62 and stationarily mounted adjacent thereto. In such case, each switch may be spring biased toward its closed position but held open by the magnet associated with it. Now, when the permanent magnet 50 rises to the 2 /2" (or 3 /2") level, its magnetism will oppose that of the switch magnet is such a Way as to render the spring bias operative to close the switch. Also, in place of the permanent magnet 50, one may employ :a magnetically permeable member (which is not a permanent magnet) and use it, as is often done, to reduce the influence of the magnetic field upon the switch and in that way render the spring bias on the switch effective to close the switch.

If clogging should occur, it will be appreciated: that the cover 3 may be raised sufiiciently to clear the upper end of rod 36 and then removed; that the entire outlet trap may be moved horizontally to free its outlet pipe from the tank outlet 9 and then lifted upwardly through the uncovered opening of the tank 1 and thereby removed from the tank; and that it is a relatively simple matter to clean and replace.

It will also be appreciated that the large number of slot-like outlets gives this trap an extremely large flow capacity, increases the length of its maintenance free operation and the purity of its effluent, effects a substantial reduction in velocity of the liquid passing through each slot and minimizes its tendency to clog. All of these objectives are accomplished in a simple inexpensive and compactly constructed trap. Since this trap may be made of plastic, it is lightweight. As must be obvious it may be easily and quickly installed and just as easily and quickly removed, inspected, cleaned and reinstalled or replaced.

Finally should the trap become partially clogged, the signal 40 will give ample warning of that condition. If clogging continues and approaches an emergency condition, the audible signal 60 will give ample warning. In any of these cases, the extent to which the rod 36 projects from the ground is enough to advise the observer thereof as to the condition of the trap.

When the ash accumulation in the bottom of septic tank 7 rises to a point where it interferes with the inflow of liquid or of sewage into the open bottom of cylinder '8, the accumulation should be removed from the tank. If, instead of being removed, it is permitted to accumulate, then the inflow of sewage into the bottom of tank 8 will carry more and more of the settled solids upwardly into tank 8. Clogging will become more frequent and the operation of the signal means will likewise become more frequent initially and more prolonged if this condition is permitted to exist. In this way the signaling means of my invention additionally gives thewarning of the desirability or necessity of cleaning out the tank.

Having described my invention, I claim:

1. An outlet trap for a septic tank comprising:

(A) a plurality of disc-dam units,

(1) each unit comprising 9 (a) a disc-like base and (b) a continuous elongate dam arranged on said base and extending from one side of said base to the other so as to separate said base into an upstream portion and a downstream portion,

(1) said downstream portion of said base being imperforate;

(2) said units being arranged in superposed stack-forming relationship such that the base of each upper over-lying unit (a) is spaced from the upper edge of the dam of the under-lying unit and (b) cooperates therewith to form a horizontally elongate vertically narrow outlet slot;

(3) spacing means for holding said units in spaced relationship, and

(4) means for holding said superposed units firmly together in stack-forming relationship;

(5) the upstream side of said trap, de-

lineated on the base of each unit by said continuous elongate darn, forming an inlet for said trap;

(6) means for closing the downstream side of said trap so as to limit communication with said upstream side of said trap to said elongate vertically narrow outlet slots; and

(7) outlet means in open communication with said downstream side of said trap.

2. The trap of claim 1 wherein:

(A) a marginal portion of the base, along a substantial portion of the upstream side of the dam, provides an upstream digestion shelf.

3. The trap of claim 2 wherein:

(A) the upstream shelf of the disc is provided with spaced, ash return perforations.

4. An outlet trap unit for a septic tank, comprising:

(A) a plurality of disc-dam units,

(1) each unit comprising (a) a disc-like base and (b) a continuous elongate darn arranged on the base,

(2) said units being arranged in superposed stackforming relationship such that the base of each overlying unit (a) is spaced from the upper edge of the dam of the underlying unit and (b) cooperates therewith to form a horizontally-elongate vertically-narrow outlet slot;

(3) means for holding said disc-dam units in spaced relationship;

(B) a vertically-arranged casing horizontally surroundsaid stack of units,

(1) the lower end portion of said casing being open to receive sewage, and

(2) the upper end portion of said casing having an outlet opening for the discharge of sewage; and

(C) means mounting said stack upon said casing (1) with a vertically-extending upstream casing chamber, between the casing and the upstream side of the dams, communicating with the lower open end portion of the casing and (2) with a vertically-extending downstream stack chamber, on the downstream side of the dams, communicating with the outlet of the casing,

(3) means for closing communication with the downstream side of said dams with the lower open end portion of said casing.

5. The outlet trap unit of claim 4 wherein:

(A) said supporting and spacing means includes a hanger bar vertically-arranged in said upstream cats- 10 ing chamber to force the stack horizontally in the direction of the casing outlet. 6. An improved septic tank type of sewage disposal means, comprising:

(a) a septic tank having an inlet, a stagnant level and and outlet;

(1) said stagnant level extending across said tank on a plane with the bottom of said outlet;

(b) an outlet trap positioned Within the tank adjacent to said outlet to separate said outlet from the main body of sewage within'the tank and to confine the normal communication of the tank outlet to the downstream side of the trap, said trap including:

(1) a series of disc-dam units in superposed stacks relation,

-(a) said disc forming the base of each unit and supporting a dam,

(b) said dam extending sinuously across said base from side to side,

(2) spacing means for each unit so that the dam of a lower unit cooperates with the base of an upper unit to form a narrow elongate outlet slot,

(3) the base of the lower disc-dam unit in the stack, extending .past said bases of said other disc-dam units to close communication of the downstream side of the trap with said tank,

(4) support means for holding said'units in superposed stack forming relation (5) said trap,

(a) projecting vertically above and below said stagnant level and,

(b) providing a series of narrow slot like outlet openings to accommodate the flow of sewage efiluent from the upstream side of the trap to the downstream side thereof, said openings extending over the vertical distance between said stagnant level and another level vertically spaced substantially from said stagnant level.

7. The disposal means of claim 6 wherein:

(A) said narrow slot-like outlet openings include one range of normally unsubmerged openings which extend from an opening adjacent said stagnant level to an opening spaced substantially above said stagnant level so that (l) the lower normally unsubmerged openings of said range accommodate the normal range of stagnant level overflows which occur when the trap is clean and unclogged, and

(2) the progressively higher openings of said range accommodate the progressively higher overflows which occur as and when the trap clogs progressively above the stagnant level.

8. The disposal means of claim 7 wherein:

(A) said narrow slot-like outlet openings include another range of normally submerged openings which extend from an opening adjacent said stagnant level to an opening spaced substantially below said stagnant level.

9. The disposal means of claim 7 including:

(A) signal means adapted, when actuated, to provide a warning signal which may be sensed outside of said septic tank; and

(B) actuating means, operating in response to said progressively higher overflows, to actuate said signal means.

10. The disposal means of claim 9 wherein:

(A) said signal means includes a silent signal capable of being observed outside of said tank, when actuated.

11. The disposal means of claim 9 wherein:

(A) said progressively higher overflows include overflows of an intermediate order and overflows of a relatively higher order;

(B) said signal means includes a silent signal capable of being observed outside of said tank and an audible signal capable of being heard outside of said tank; and

(C) said actuating means includes (1) means to actuate said silent signal in response to overflows of said intermediate order, and

(2) means to actuate said audible signal in response to overflows of said higher order.

12. An improved septic tank type of sewage disposal means, comprising:

(A) a septic tank having an inlet, a stagnant level, and

an outlet, 7

(1) said stagnant level extending across the tank on a plane with the bottom of said outlet;

(B) the outlet trap unit of claim 4; and

(C) means mounting said trap unit within the tank (1) with said vertically-extending downstream stack chamber and said casing outlet communicating with said tank outlet,

(2) with said stagnant level extending into said upstream stack chamber at an elevation corresponding to the bottom side of said tank outlet .and

(3) with the top and bottom slot-like openings of the stack respectively extending substantially above and substantially below said stagnant level.

13. An improved septic tank type of sewage disposal means comprising:

(a) a septic tank having an inlet, an outlet and a stagnant level,

(1) said stagnant level lying on a horizontal plane with the bottom of said outlet;

(b) an outlet trap positioned within the tank adjacent to said outlet, to separate said outlet from the main body of sewage within the tank and to confine the normal communication of the tank outlet to the downstream side of the trap, said trap including:

(1) a plurality of units arranged in superposed stack forming relation,

(2) each unit containing a base and a continuous raised darn,

(3) spacing means for spacing the base of an upper unit from the top of the dam of a lower unit to form a narrow elongate slot-like opening 12 (4) means for holding said units together in stack forming relation, and (5) a vertically arranged casing surrounding said stack of units,

(a) the upper end portion of said casing having an outlet opening in communication with said tank outlet (6) said trap having an inlet from the bottom (a) the inlet being in open communication with the main body of sewage within the tank (7) said trap being vertically disposed so that the lower end projects below said stagnant level and the upper end projects above said stagnant level, and providing said slot-like openings for the flow of sewage effluent from the upstream side of the trap to the downstream side, including:

(a) at least one normally unsubmerged slotlike opening which accommodates normal stagnant level over-flow when the trap is clean and unclogged, and

'(b) a higher normally unsubmerged slot-like opening which accommodates the progressively higher over-flows which occur as and when the trap clogs successively above the stagnant level.

14. The disposal means of claim 13, including: (a) warning means extending through said tank and Within said casing and responsive to said higher overflows,

References Cited UNITED STATES PATENTS 2,216,646 10/1940 Mautz 210-488 X 2,884,131 4/1959 Mocarski 210S32 X 2,900,084 8/1959 Zabel 210-460 2,959,287 11/1960 Davis et al. 210-488 X 3,006,478 10/1961 Mueller 210488 X 3,025,962 3/1962 Williams 210-86 3,037,633 6/1962 Veitel et al. 210-488 X REUBEN FRIEDMAN, Primary Examiner. SAMIH N. ZA-HARNA, Examiner. 

1. AN OULET TRAP FOR A SEPTIC TANK COMPRISING: (A) A PLURALITY OF DISC-DAM UNITS, (1) EACH UNIT COMPRISING (A) A DISC-LIKE AND (B) A CONTINUOUS ELONGATE DAM ARRANGED ON SAID BASE AND EXTENDING FROM ONE SIDE OF SAID BASE TO THE OTHER SO AS TO SEPARATE SAID BASE INTO AN UPSTREAM PORTION AND A DOWNSTREAM PORTION, (1) SAID DOWNSTREAM PORTION OF SAID BASE BEING IMPERFORATE; (2) SAID UNITS BEING ARRANGED IN SUPERPOSED STACK-FORMING RELATIONSHIP SUCH THAT THE BASE OF EACH UPPER OVER-LYING UNIT (A) IS SPACED FROM THE UPPER EDGE OF THE DAM OF THE UNDER-LYING UNIT AND (B) COOPERATES THEREWITH TO FORM A HORIZONTALLY ELONGATE VERTICALLY NARROW OUTLET SLOT; (3) SPACING MEANS FOR HOLDING SAID UNITS IN SPACED RELATIONSHIP, AND 